Stencil system claims best of both worlds

Soldering & Surface Mount Technology

ISSN: 0954-0911

Article publication date: 1 December 2004




(2004), "Stencil system claims best of both worlds", Soldering & Surface Mount Technology, Vol. 16 No. 3.



Emerald Group Publishing Limited

Copyright © 2004, Emerald Group Publishing Limited

Stencil system claims best of both worlds

Stencil system claims best of both worlds

Keywords: Stencils

A novel stencil system is claimed to combine all the advantages of both foils and frames without any of the drawbacks and the lowest wear rates for lead-free processes. An innovative new development from stencil manufacturing specialist Tannlin offers a viable alternative to both remountable foils and framed stencils in surface mount technology.

The company’s VectorGuard quick-mount foil technology combines the cost and space saving advantages associated with foils, with the durability and ease of handling provided by frames. VectorGuard also provides extremely low wear rates that are especially desirable in lead-free manufacturing processes. Remountable foils have been popular with electronic manufacturers because of their space and cost saving benefits, but a major drawback is the difficulty of handling them safely.

According to the Health and Safety Executive, one third of all injuries in engineering are caused by cuts from sharp metal during handling. “The trouble is that traditional surface mount foils are much like giant razor blades”, says Fraser Shaw, Tannlin’s Director of Sales and Marketing. Framed stencils, on the other hand, offer greater protection for the stencil and handler, but they are far more bulky, making them difficult to handle and store. All these issues are addressed by Tannlin’s VectorGuard quick-mount foil stencil system, which has been designed specifically to address the health and safety issues surrounding remountable foils while providing the protection of a frame. The system comprises a highly accurate, laser-cut foil supplied ready-mounted in a lightweight, rigid aluminium extrusion measuring only 5 mm thick. The slimline “frame” makes handling easier and protects employees from health and safety issues. It also protects the edges of the stencil from damage and prevents the body from creasing. So, not only does VectorGuard extend the life of the stencil, but it is also quick and easy to mount. At the heart of the system is a highly accurate, laser-cut foil made of high-durability, very low wear rate steel.

The foils are produced in an environmentally friendly way that avoids the need for any harsh, etching chemicals. This is because VectorGuard has been cleverly designed so that the foil is held in its mini-frame by a strong mechanical bond. It does not require locating holes to be etched into the metal, as standard foils do, and can, therefore, be made of a much tougher and harder grade of steel. Low wear rates can be important in lead-free processes, where manufacturers have found stencil wear rates are much higher than for standard tin-lead pastes. This may be due to a number of factors, most notably that squeegee pressures can be higher for lead-free, while the lead in tin-lead may act as a useful lubricant during the print process.

A typical etched foil could wear out after 10,000 prints using lead-free paste, but Tannlin’s laser cut VectorGuard has been shown to last for up to 60,000 prints. Tannlin is unique among stencil manufacturers as it is the only company to have designed and built its own laser-cutting equipment specifically to make stencils for the electronics industry. The company’s Managing Director, Graham Hall, produced the industry’s first ever laser-cut stencil in 1989, giving it a head start with the technology, and Tannlin is now the fastest growing stencil supplier in the UK.

This depth of experience is vital, because a laser-cutting machine is nothing without knowing how to achieve the best possible results. “There are good lasers and bad lasers, and many things that can go wrong”, says Shaw. “But with our purpose built machines, we can offer a cutting resolution of 0.1 um, making Tannlin VectorGuard the most accurate element of the SMT production line by far”.

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